Automatic injection devices for delivering active substances (e.g. pen-type injectors) are well known in the art. In many cases, training versions of such devices are required for showing potential users (e.g., patients or healthcare providers) how a device should be employed and for illustrating the advantages of the device. Such devices are frequently called “promotion” or “training” devices. The devices should mimic the function of a corresponding real injection device, but should not be capable of injecting an active substance.
Document U.S. Pat. No. 5,071,353 describes a training device for an automatic injector. The device comprises a cylindrical outer sleeve in the rear position of which a discharge mechanism is connected. The discharge mechanism comprises a plunger, a coil spring which acts on the plunger, a locking device, and a safety member. However, this device does not provide means allowing an accurate simulation of the resistance acting on the discharge mechanism of a regular injection device when an active substance is ejected.
WO 2011/151315 discloses a training cartridge for a drug delivery device as well as a method for resetting the cartridge. The cartridge comprises a body of substantially cylindrical shape, a piston that is slidably disposed in the body in an axial direction, and a closure means disposed at an axial end portion of the body. The piston and the closure means confine an interior volume coupled to the exterior via at least one fluid escape channel. According to the method disclosed, several steps are required for resetting the cartridge.